blob: 7ab3ceabd138e78a3ef1f783614fd38660de678e [file] [log] [blame]
// Copyright 2013 Google Inc. All Rights Reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
// Declares a utility class for getting and storing quick and dirty stack
// captures.
#include <windows.h>
#include "base/logging.h"
#include "syzygy/common/asan_parameters.h"
namespace agent {
namespace asan {
// Computes the hash of a given stack trace. The hash function is simply an add
// of all the stack trace pointers.
uint32 ComputeStackTraceHash(void** stack_trace, uint8 stack_depth);
// A simple class for holding a stack trace capture.
class StackCapture {
// From,
// The maximum number of frames which CaptureStackBackTrace can be asked
// to traverse must be less than 63, so set it to 62.
static const size_t kMaxNumFrames = 62;
// The type used for reference counting. We use saturation arithmetic, so it
// will top out at kMaxRefCount.
typedef uint16 RefCount;
static const RefCount kMaxRefCount = -1;
// This corresponds to the the type used by ::CaptureStackBackTrace's hash
// for a stack-trace.
typedef ULONG StackId;
COMPILE_ASSERT(sizeof(StackId) == sizeof(common::AsanStackId),
: ref_count_(0), stack_id_(0), num_frames_(0),
max_num_frames_(kMaxNumFrames) {
explicit StackCapture(size_t max_num_frames)
: ref_count_(0), stack_id_(0), num_frames_(0), max_num_frames_(0) {
DCHECK_LT(0u, max_num_frames);
DCHECK_GE(kMaxNumFrames, max_num_frames);
max_num_frames_ = max_num_frames;
// Static initialisation of StackCapture context.
static void Init();
// Calculate the size necessary to store a StackCapture with the given
// number of stack frames.
// @param max_num_frames The maximum number of stack frames the object needs
// to be able to hold.
// @returns the size of a StackCapture object with the given number of frames.
static size_t GetSize(size_t max_num_frames);
// Calculate the max number of frames that can be fit into a memory region of
// the given size.
// @param bytes The number of bytes to be used.
// @returns the maxmimum number of frames that will fit in the provided number
// of bytes.
static size_t GetMaxNumFrames(size_t bytes);
// @returns the size of this initialized StackCapture object.
size_t Size() const { return GetSize(max_num_frames_); }
// @returns true if this stack trace capture contains valid frame pointers.
bool IsValid() const { return num_frames_ != 0; }
// Increments the reference count of this stack capture.
void AddRef();
// Decrements the reference count of this stack capture.
void RemoveRef();
// @returns true if the reference count is saturated, false otherwise. A
// saturated reference count means that further calls to AddRef and
// RemoveRef will be nops, and HasNoRefs will always return false.
bool RefCountIsSaturated() const { return ref_count_ == kMaxRefCount; }
// @returns true if this stack capture is not referenced, false otherwise.
bool HasNoRefs() const { return ref_count_ == 0; }
// @returns the reference count for this stack capture.
RefCount ref_count() const { return ref_count_; }
// @returns the ID associated with this stack trace.
StackId stack_id() const { return stack_id_; }
// @returns the number of valid frame pointers in this stack trace capture.
size_t num_frames() const { return num_frames_; }
// @returns the maximum number of valid frame pointers in this stack trace
// capture.
size_t max_num_frames() const { return max_num_frames_; }
// @returns a pointer to the stack frames array, or NULL if the array has a
// size of 0.
const void* const* frames() const {
return max_num_frames_ != 0 ? frames_ : NULL;
// Sets the stack ID for a given trace.
// @param The stack ID to set.
void set_stack_id(StackId stack_id) { stack_id_ = stack_id; }
// Set the number of bottom frames to skip per stack trace. This is needed to
// be able to improve the stack cache compression in Chrome's unittests where
// the bottom of the stack traces is different for each test case.
// @param bottom_frames_to_skip The number of bottom frames to skip.
static void set_bottom_frames_to_skip(size_t bottom_frames_to_skip) {
CHECK_LT(bottom_frames_to_skip, kMaxNumFrames);
bottom_frames_to_skip_ = bottom_frames_to_skip;
// Get the number of bottom frames to skip per stack trace.
static size_t bottom_frames_to_skip() { return bottom_frames_to_skip_; }
// Initializes a stack trace from an array of frame pointers, a count and
// a StackId (such as returned by ::CaptureStackBackTrace).
// @param stack_id The ID of the stack back trace.
// @param frames an array of frame pointers.
// @param num_frames the number of valid frame pointers in @frames. Note
// that at most kMaxNumFrames frame pointers will be copied to this
// stack trace capture.
void InitFromBuffer(StackId stack_id,
const void* const* frames,
size_t num_frames);
// Initializes a stack trace using ::CaptureStackBackTrace. This is inlined so
// that it doesn't further pollute the stack trace, but rather makes it
// reflect the actual point of the call.
__forceinline void InitFromStack() {
num_frames_ = ::CaptureStackBackTrace(
0, max_num_frames_, frames_, NULL);
if (num_frames_ > bottom_frames_to_skip_)
num_frames_ -= bottom_frames_to_skip_;
num_frames_ = 1;
stack_id_ = ComputeStackTraceHash(frames_, num_frames_);
// The hash comparison functor for use with MSDN's stdext::hash_set.
struct HashCompare {
static const size_t bucket_size = 4;
static const size_t min_buckets = 8;
// Calculates a hash value for the given stack_capture.
size_t operator()(const StackCapture* stack_capture) const;
// Value comparison operator.
bool operator()(const StackCapture* stack_capture1,
const StackCapture* stack_capture2) const;
// Computes the hash of a stack trace using relative addresses of each stack
// frame.
// @returns the relative hash of this stack trace.
StackId ComputeRelativeStackId();
// The number of bottom frames to skip on the stack traces.
static size_t bottom_frames_to_skip_;
// The unique ID of this hash. This is used for storing the hash in the set.
StackId stack_id_;
// The number of valid frames in this stack trace capture, and the maximum
// number it can represent. We use uint8s here because we're limited to
// kMaxNumFrames by the OS machinery and want this data structure to be as
// compact as possible.
uint8 num_frames_;
uint8 max_num_frames_;
// The reference count for this stack capture. We use saturation arithmetic
// and something that is referenced 2^16 - 1 times will stay at that reference
// count and never be removed from the stack cache.
RefCount ref_count_;
// The array or frame pointers comprising this stack trace capture.
// This is a runtime dynamic array whose actual length is max_num_frames_, but
// we use the maximum length here so that other users of StackCapture can
// capture full stack traces if they so desire.
// NOTE: This must be the last member of the class.
void* frames_[kMaxNumFrames];
} // namespace asan
} // namespace agent